Patent Literature 1 discloses a fuel injector in which either a seat portion of a valve body or a valve seat of a valve seat formation portion is formed of an elastic member. Further, Patent Literature 1 also discloses a technique for providing a stopper for restricting movement of the valve body toward the valve seat when a predetermined increase in stroke of the valve body is reached even though the seat portion is repeatedly attached on and detached from the valve seat to generate a compression permanent deformation in the elastic member.
Patent Literatures 2 and 3 disclose a gas cutoff valve in which a valve body is provided with a seal member formed of elastic material, and being attachable/detachable on/from a valve seat. As described in Patent Literature 2, a sizing portion is provided on the valve seat for defining a crushing margin of the seal member when the seal member sits on the valve seat. Thus, the crushing margin of the seal member is defined upon closing the valve.
In the fuel injector disclosed in Patent Literature 1, however, the stroke of the valve body immediately after manufacturing the fuel injector differs from that of the valve body after the compression permanent deformation occurs in the elastic member, which varies a quantity of the fuel injected. Specifically, by repeatedly opening and closing the fuel injector, the elastic member may wear, so that the crushing margin may be varied. Also, a variation in fuel pressure may vary the crushing margin of the elastic member.
The cutoff valve disclosed in Patent Literature 2, upon closing the valve, the valve body is abutted against the sizing portion (protrusion) to stabilize the crushing margin of the seal member. Even in use of the elastic member as the seal member, the changes in stroke of the valve body can be suppressed. In the cutoff valve, however, the sizing portion for defining the crushing margin of the seal member is integral with a member for forming the valve seat on which the seal member is to sit. In use of the sizing portion for defining the crushing margin of the seal member, the crushing margin depends on the relative positions of the sizing portion and the valve seat in the direction along the movement direction of the valve body. When the sizing portion and the valve seat are formed from one member, even though the dimensional accuracy of the sizing portion and valve seat is enhanced, a large dimension error of the seal member may vary the crushing margin of an individual product. In order to set the crushing margin to the same level for each product, the dimensional accuracy of the seal member has to be enhanced in the same way as other components. However, in general, it is difficult to improve the dimensional accuracy of the elastic member.